Is this really a useful thing to do .. ??
Both Canon and Nikon have this facility in their higher end bodies under different names; AF Microadjustment in Canon and AF Fine-Tune in Nikon.
If pictures from your camera, lens or combination are lacking proper focus, it may be that camera, lens, or both are causing front or back focusing.
Common sense dictates making sure that any focusing problems are investigated to make sure that it is well and truly a problem that requires at least fine tuning, or if more serious sending the camera or lens back for servicing or exchange.
Rumours about quality control for cameras and lenses indicate they would pass the test as long as any focusing variations fall within the depth of field at a given focal length, aperture and focal distance.
All said .. if you find that your lens is either front or back focusing enough at a given focal length, aperture and distance (usually longest focal length in zoom, wide open, and at the minimal focusing distance as DOF is shallowest) then fine-tuning or micro-adjustment is going to be helpful.
From several resources on the internet I gathered the following, and others may differ;
1- Calibrate a zoom using the longest focal length (the tele end of the zoom range)
2- Use the maximum aperture (wide open)
3- Use 25-50x focal length in mm as testing distance between camera and target
4- Use tripod, mirror-up and remote shutter release
5- If you print your own target sheet, do it on inkjet and not laser
6- Do 3 shots per adjustment
7- Do +/- adjustments and keep doing this until you narrow down your adjustment
8- Use JPEG’s or RAW without any adjustments
9- Use a standard target (DataColor© SpyderLensCal© or Michael Tapes Design© LensAlign©)
10- Use computer software (Michael Tapes Design© FocusTune© or Reikan© FoCal©) to decide the best adjustment value
11- Target chart should be contrasty, well illuminated and dead square and parallel to the camera/sensor
12- Set focus to central point and single autofocus after manually focusing at the centre of the target
13- Between shots, set the lens focus to infinity
14- Set image stabilisation off
15- Set ISO to lowest possible for best results
Remember that only one sample of a certain lens can be registered in the camera at any one time, and that the adjustment is saved in the camera. Also, if all the lenses register the same result, it is probably the camera body that needs to be adjusted for all the lenses.
I have to say that I have not tried this complete setup myself yet .. but tried the cheap way .. using a printed focus target sheet on a wall and also tried it on a floor or table with camera at 45 degrees, and I failed on both occasions to achieve a result that would produce better focused and sharper photos in real life after the calibration. I went out with my camera and shot handheld and on tripod real life shots with and without calibration and I have to say I have not seen an improvement .. so maybe the cheap way is not valid or reliable and maybe the more methodical way stated above would be more useful .. I would certainly be interested in hearing from regular photographers who have done that and noticed an improvement .. So please let me know your experiences before I go out to buy all this kit!!
Here are some internet resources ..